In the first broad-scale study of rivers throughout the Midwest, the USGS has found neonicotinoids, the suspected bee-killing pesticides, widespread in rivers and streams.

The study tested nine rivers and streams -- including the Mississippi and Missouri Rivers -- draining parts of Iowa, Minnesota, Montana, Nebraska, North Dakota, South Dakota, and Wisconsin. Most corn and soybean planted in these states now comes delivered with a prophylactic coating of pesticides -- like antibiotics in CAFOs, the pesticides are used regardless of whether they are needed or not.

The scientists detected increased concentrations after rains, consistent with a theory that the pesticide is being flushed from soils by the precipitation. Such increases were found even before the first planting of the year, indicating that the pesticide sticks around in the soils, providing a continuous source to replenish the rivers year-round.

The neonicotinoid pesticides, sometimes called neonics, were intended to be poisonous to crop pests but of low toxicity to vertebrates. [In spite of their relationship with nicotine, the EPA considers these chemicals as not likely to cause cancer in humans.]

One of the chemicals, imidacloprid, is known to be toxic to aquatic organisms at 10-100 nanograms per liter if the aquatic organisms are exposed to it for an extended period of time. Clothianidin and thiamethoxam behave similarly to imidacloprid, and are therefore anticipated to have similar effect levels. Maximum concentrations of clothianidin, thiamethoxam and imidacloprid measured in this study were 257, 185, and 42.7 nanograms per liter, respectively.

Clothianidin, was found in 75% of the tested locations while thiamethoxam and imidacloprid was found in 47% and 23% of the sites sampled, respectively. Two others, acetamiprid and dinotefuran, were found in only one sample each. Interestingly, the sixth neonic thiacloprid, was not found in any of the tested samples -- perhaps supporting Bayer's case against pesticide bans, such as the action against neonicotinoids in Europe which is experimenting with growing crops neonic-free through 2016 in order to get a better picture of the risks versus benefits of these widespread agrichemicals.

The study, “Widespread occurrence of neonicotinoid insecticides in streams in a high corn and soybean producing region, USA” appears in Environmental Pollution [Volume 193, October 2014, Pages 189–196].